Shoe sewing machine



1933- D. L. BUNKER 1,923,139

- SHOE SEWING MACHINE Original Filed Feb. 11, 1929 Wiffiess Patented Aug. 22 1933 SHOE SEWING MACHINE- Dinsmore L. Bunker, Auburn, Maine, assignor to United Shoe Machinery Corporation, Paterson, N. J., a Corporation of New Jersey Application February 11, 1929, Serial No. 339,011

Renewed June 1, 1932 6 Claims.

The present invention relates to inseam shoe sewing machines, and in particular to the means for locking and releasing the back gage or welt guide and the back rest employed in such machines.

The back rest and the back gage, or in a welt sewing machine the welt guide which takes the place of the latter, are mounted or controlled by slides and cooperate to steady the shoe during the entry of the needle thereinto, and act as abutments to hold the shoe against the pull of the needle and the thread as the needle is retracted. During the work-feeding operation, these gage and rest devices are customarily respectively retracted and released to permit free feeding of the shoe and to prevent marring of theupper through contact of the irregular edges of the welt guide therewith while the shoe is in motion. At the end of the feeding movement, the gage and the rest move forward into contactwith the shoe, and for the most accurate and effective manipulation of the shoe by the operator must be firmly locked against the ensuing rearward pressure of the work at the precise point in their forward travel at which they encounter said shoe. The location of this point varies at different points in the shoe. This locking and subsequent unlocking action must accompany each stitch formed by the machine, and the locking mechanism thus must be capable of performing its function without loss of its efficiency in the face of hard usage and consequent wear of parts.

The primary object of the invention is to produce simple and improved means for securing the back gage or welt guide and the back rest in the exact positions in which they are brought to rest through contact with the work at the completion of their forward movement.

With this object in View, the invention comprises the combination with the back gage slide and with the back rest slide, of a toggle-joint arranged with the ends'of its arms bearing against the respective slides, to force them laterally against their guideways and thus to clamp them immovably'in position.

Another object of the invention is to provide locking mechanism for the aforesaid slides which shall not be quickly rendered ineffective through wear in the face of the hard service which it is called upon to perform.

To this end, the invention also comprises the provision upon the ends of the toggle-arms which engage the slides, of working faces which are cam-shaped to compensate for looseness of fit of 5 the cooperating parts arising through wear or toggle-joint. This shift not only distributes the through other causes. Through this provision, the points of contact, or tangency, between the said working faces and the slides shift along the cams in proportion to the increased distance between said slides when forced apart by the wear upon the cam-faces, but through increasing the effective length of each toggle-arm permits the toggle-joint to maintain the same effective angular relation of its arms which provides the most advantageous leverage. even though the spacing of the slides be gradually changing. Each toggle-arm is caused to act as a cam rotated about a point substantially in the opposing slideedge as a center by the actuating force which is applied at the joint of the toggle-joint, and as the said joint is moved farther to clamp the slide as wear occurs, the point of tangency moves an exactly corresponding amount in the same direction, so that the effective angular relation of the toggle-arm remains unchanged within the limits of the structure.

In addition to the features of invention above referred to, the invention also consists in the devices, combinations and arrangements of parts hereinafter described and claimed, certain of which, while particularly adapted for use in connection with the slides of the back gage and back rest of an inseamsewing machine are not limited to such use, but may be employed to lock a single slide or the slides of work supports other than the back gage and back rest.

The features of the invention will be readily understood through reference to the accompanying drawing, illustrating a machine embodying the invention in its'preferred form, and to the following detailed description of the same.

In the drawing:

Fig. 1 is a view in sideelevation of a portion of a welt sewing machine embodying the invention; Fig. 2 is a detail view in side elevation showing portions of the back gage or welt guide slide and of the back rest slide, and of the slotted cover-plate, with the toggle-joint locking device and its actuating means in locked relation; Fig. 3 is a detail rear elevation of the partsof Fig. 2; Fig.4 is an edge view of one of the cam-faced toggle-arms; Fig. 5 is a more or less diagrammatic illustration showing on a large scale a toggle-arm in locking relation with its slide.

The machine illustrated in the drawing, is provided with a curved hook needle, a needle guide, a looper, a threadarm, a take-up, a channel guide, a welt guide, a back rest, and back rest and welt guide slides, all having the same construction, arrangement and mode of Operation as the corresponding parts of the welt sewing machine disclosed in U. S. Patent No. 1,108,560,

dated Aug. 25, 1914 to A. Eppler, for Shoe sewing machine. For a full and complete description of the parts not fully described herein, reference may be had to said patent.

The back rest of the illustrated machine is in dicated at 1, mounted at the forward end of its slide 2 which is mounted to move back and forth in guideways 3 formed for it in the frame of the machine. The welt guide 4 is combined by a link 5 with its slide 6 which is adapted to be moved back and forth in guideways 7 in the machine frame.

The improved locking mechanism'shown herewith for holding the back rest slide 2 and the welt guide slide 6 in their extreme forward positions comprises a toggle-joint arrangement of two similar arms 8 disposed between and bearing against the adjacent edges of the respective slides 2 and 6. The joint ends 9 of these arms are formed with half-round surfaces which are received within correspondingly shaped recesses oppositely disposed in an actuating member 10 and which rock freely in said recesses in a manner to act as the joint or knuckle of the toggle-joint. The said actuating member 10 is combined by means of a pivot-pin 11 with 'an arm of a bellcrank 12 pivotally mounted at 13 and receiving periodic actuation through engagement of its roll 14 with the periphery of a disc cam 2'7 on the shaft 16 of the machine, whereby the actuating member is moved positively a slight distance in a rearward direction, carrying with it the portions 9 of the arms and bending the joint to unlock the slides. A contracting spring 15 is combined with the pivot-pin 11 and anchored at '36 to provide a force yieldingly acting to move the actuating member 10 forwardly. This forward movement tends to straighten the togglelink by bringing the portions 9 of the arms 8 toward the dead center line joining the two contact points 17 where the ends of the arms engage their respective slides, and through the increase in the effective length of the whole toggle-joint resulting from this straightening the slides 2 and 6 are forced away from each other powerfully and clamped against their guideways.

With the toggle-arm 8 in locked relation, each arm is supported in its pressure against its slide practically entirely by the equal and opposite pressure of its companion arm, the only component of pressure falling on the actuating member 10 being that resulting from the small angular reserve, about 5 degrees, between the dead center line and the effective angle of either arm, which is set as the limit of approach permitted the joint of the toggle-joint in its movement toward the dead center line.

The. toggle-arms 8 look their respective slides with their maximum intended power when they arrive at this angular relation of substantially 5 degrees with respect to the dead center line and the joint is stopped in its forward movement by the resistance of the slides to being forced fur ther apart. Obviously, a very slight amount of wear or looseness in the fit of the various combined parts would destroy, this angular relationship and the efficiency of the locking device, but for the provision of special means of compensation therefor. Such means is provided in the present invention by equipping the slide-engaging ends of the arms 8 with cam-faces 18, Figs. 4'and 5, so laidout that any increase in the spacing-apart of the two slides 2 and 6 permitting increased forward travel of the joint or knuckle of the toggle-joint will result in a rolling action of the cam-face along its slide which will shift the point of contact or tangency between slide and cam-surface an equal amount in the same direction, and hence the effective angular relation of the arms to the dead center line remains unchanged. Referring to Fig. 5 for an example, if the toggle arms are installed to make locking contact with the slide 6 at 17 and swing about centers such as 19 with respect to the movable actuating member 10, the effective angular relation of the arm will be such as shown by line 17-19. If wear results allowing the engaged surface of the slide 6 to rise to the position indicated bythe dotted line 21, the lower pivoting center of arm 8 will be carried forward by the actuating member 10 from point 19 to point 22, while the point of contact or tangency shifts along the cam from point 17 to point 20, a distance which makes the line 2022 (representing the effective angular relation of the arm 8) parallel to line 17-49. In other words, the effective length of the toggle-arm 8 increases without changing the effective angular relation of the arm to the dead center line.

The cam-surface is a simple one, that illustrated herein being a segment of a circle struck about center 0 and having the radius R.

The toggle-arms 8 are positioned in gaps cut.

tions 24 or pivots each having its axis substantially level with the cam-surface and disposed transversely thereto. These pivots 24 overlap the vertical sides of the slides 2 and 6, and fit into vertical portions of slots 25 formed for them in a cover-plate 26, the slots forming guideways to confine the axes of said pivots 24 to movement up and down along the'line X, Fig. 5 transverse to the direction of movement of the slides as the toggle-joint is locked and unlocked in use. The axis of each pivot 24 is the axis or center in space about which each toggle-arm swings as the actuating member 10 is moved, and this center, when the toggle-joint is locked, lies substantially in the plane of the slides surface which is engaged by the arm, though for practical reasons, such as looseness of fit of the pivots 24 in slots 25, the center may be made a small distance above the cam surface to secure a slight thrusting of the slides toward the work in looking. The arms are controlled at both their ends by forces ample to insure their being'put into and removed from operative relation with the slides at each locking and unlocking operation.

The improved means described provides a locking device adapted to clamp each slide with certainty in precisely the position in which it is brought to rest by contact with the shoe, and to hold said slides with a firmness amply sufficient to meet the requirements, the action being characterized by absence of all preliminary slip or arm rotates, and a guideway for said pivot permitting the arm to follow the deviation of the slide as the latter is pressed against its guide- Way.

2. An inseam shoe sewing machine having, in combination, a work-supporting slide, a guideway for said slide, and a toggle-arm engaging said slide and rotatable about an axis in the plane of the engaged surface of said slide to clamp the slide against its guideway, a pivot defining said axis, and a guideway for said pivot permitting the toggle-arm to follow the slide as the latter is forced against its own guideway.

3. An inseam shoe sewing machine having, in combination, a work supporting slide, a togglearm adapted to exert pressure laterally against said slide to lock the latter, and a guideway directing the movement of the working end of said toggle-arm in a path transversely disposed with respect to said slide.

4. An inseam shoe sewing machine having, in combination, a hack gage slide and a back rest slide, guideways for said slides, and locking means to fix said slides in their guideways comprising a toggle-joint disposed between said slides with its ends adapted to engage the respective slides,

guideways directing the movement of the slide engaging ends of the toggle-joint in paths transversely disposed with respect to the slides, means yieldingly acting to straighten the joint and lock the slides, and means acting to bend the joint and release the slides.

5. An inseam shoe sewing machine having, in combination, a back gage slide and a back rest slide, guideways for said slides, and locking means to fix said slides in their guideways comprising a toggle-joint disposed between said slides with its ends adapted to engage the respective slides, guideways directing the movement of the slide engaging ends of the toggle-joint in paths transversely disposed with respect to the slides, and means for actuating the joint to lock and unlock the said slides.

6. An inseam shoe sewing machine having, in combination, .a work supporting slide, a togglearm adapted to exert pressure laterally against said slide to lock the latter and having a working face cam-shaped to compensate for wear, and a guideway directing the movement of the working end of said toggle-arm in a path transversely disposed with respect to said slide.

DINSMORE L. BUNKER. 

